A passive entry system (PES) is widely known (see e.g., patent documents 1 and 2). There is a tendency to add a sensor for recognizing approach and contact of a user to a handle (hereinafter referred to as an outer handle), which is arranged on an outer side of a vehicle, to such a passive entry system. This sensor is a sensor functioning as a switch for performing unlocking and locking by the recognition result of the approach and the contact of the user. The sensor referred to herein is configured by a detection unit for outputting a predetermined detection amount as an electrical signal or the like, and a recognition unit for recognizing the approach and the contact of a human from the electrical signal or the like from the detection unit.
There are a number of methods related to the control of unlocking and locking in the passive entry system. For instance, a method of individually arranging a detection unit for unlocking and for locking individually, and unlocking according to a recognition result from a recognition unit based on the signal from the detection unit for unlocking and locking according to the recognition result from the recognition unit based on the signal from the detection unit for locking (hereinafter referred to as an individual detection control method) (see e.g., patent documents 1 and 2). A method of arranging one detection unit, and locking a door if in an unlocked state and unlocking a door if in a locked state according to a recognition result from a recognition unit based on a signal from the detection unit (hereinafter referred to as a single detection control method).
In patent document 1, the individual detection control method of attaching the respective detection unit for unlocking and for locking to different positions of the outer handle is proposed. In patent document 2, one detection unit is arranged for each of the front and the back of the outer handle with respect to one recognition unit. The individual detection control method in which the proximity (spaced apart by a predetermined short distance without contact) and the contact of a human are recognized by the signal from each detection unit in the recognition unit, and unlocking is carried out when recognized with the signal from the detection unit on the front and locking is carried out when recognized with a signal from a back electrode is proposed.
An electrostatic capacity sensor, and the like correspond to the sensor for recognizing the proximity and the contact.
The electrostatic capacity sensor is a sensor that uses a change in an electrostatic capacity involved in a change in a distance with a detecting object when the electrostatic capacity is formed between itself and the detecting object (hand approaching the vehicle herein), and that includes an electrostatic capacity→voltage conversion unit, that is, a detection unit for outputting a voltage proportional to the distance as a detection signal.
A sensor for recognizing the approach (spaced apart by a distance distant to a certain extent) is also known, which may be an electric wave sensor, and the like.
The electric wave sensor is a sensor that uses a time difference between a transmission wave and a reception wave that returns when reflected by an object, and that includes a detection unit for outputting a predetermined electric signal as a detection signal when the object enters a detection region. The detection region herein means a range of detection distance to a predetermined detecting object.    Patent document 1: Japanese Unexamined Patent Publication No. 2002-295094    Patent document 2: Japanese Unexamined Patent Publication No. 2004-92027